Showing papers on "Electric power published in 2009"

False data injection attacks against state estimation in electric power grids

Abstract: A power grid is a complex system connecting electric power generators to consumers through power transmission and distribution networks across a large geographical area. System monitoring is necessary to ensure the reliable operation of power grids, and state estimation is used in system monitoring to best estimate the power grid state through analysis of meter measurements and power system models. Various techniques have been developed to detect and identify bad measurements, including the interacting bad measurements introduced by arbitrary, non-random causes. At first glance, it seems that these techniques can also defeat malicious measurements injected by attackers.In this paper, we present a new class of attacks, called false data injection attacks, against state estimation in electric power grids. We show that an attacker can exploit the configuration of a power system to launch such attacks to successfully introduce arbitrary errors into certain state variables while bypassing existing techniques for bad measurement detection. Moreover, we look at two realistic attack scenarios, in which the attacker is either constrained to some specific meters (due to the physical protection of the meters), or limited in the resources required to compromise meters. We show that the attacker can systematically and efficiently construct attack vectors in both scenarios, which can not only change the results of state estimation, but also modify the results in arbitrary ways. We demonstrate the success of these attacks through simulation using IEEE test systems. Our results indicate that security protection of the electric power grid must be revisited when there are potentially malicious attacks.

Overview of current and future energy storage technologies for electric power applications

Abstract: In today's world, there is a continuous global need for more energy which, at the same time, has to be cleaner than the energy produced from the traditional generation technologies. This need has facilitated the increasing penetration of distributed generation (DG) technologies and primarily of renewable energy sources (RES). The extensive use of such energy sources in today's electricity networks can indisputably minimize the threat of global warming and climate change. However, the power output of these energy sources is not as reliable and as easy to adjust to changing demand cycles as the output from the traditional power sources. This disadvantage can only be effectively overcome by the storing of the excess power produced by DG-RES. Therefore, in order for these new sources to become completely reliable as primary sources of energy, energy storage is a crucial factor. In this work, an overview of the current and future energy storage technologies used for electric power applications is carried out. Most of the technologies are in use today while others are still under intensive research and development. A comparison between the various technologies is presented in terms of the most important technological characteristics of each technology. The comparison shows that each storage technology is different in terms of its ideal network application environment and energy storage scale. This means that in order to achieve optimum results, the unique network environment and the specifications of the storage device have to be studied thoroughly, before a decision for the ideal storage technology to be selected is taken.

Microgrids and Active Distribution Networks

Abstract: Microgrids and Active Distribution Networks offer a potential solution for sustainable, energy-efficient power supply to cater for increasing load growth, supplying power to remote areas, generation of clean power and reduction in emission of greenhouse gases & particulates as per Kyoto protocol.

A Survey of Particle Swarm Optimization Applications in Electric Power Systems

Abstract: Particle swarm optimization (PSO) has received increased attention in many research fields recently. This paper presents a comprehensive coverage of different PSO applications in solving optimization problems in the area of electric power systems. It highlights the PSO key features and advantages over other various optimization algorithms. Furthermore, recent trends with regard to PSO development in this area are explored. This paper also discusses PSO possible future applications in the area of electric power systems and its potential theoretical studies.

State-of-Charge (SOC)-Balancing Control of a Battery Energy Storage System Based on a Cascade PWM Converter

Abstract: Renewable energy sources such as wind turbine generators and photovoltaics produce fluctuating electric power. The fluctuating power can be compensated by installing an energy storage system in the vicinity of these sources. This paper describes a 6.6-kV battery energy storage system based on a cascade pulsewidth-modulation (PWM) converter with focus on a control method for state-of-charge (SOC) balancing of the battery units. A 200-V, 10-kW, 3.6-kWh (13-MJ) laboratory system combining a cascade PWM converter with nine nickel metal hydride (NiMH) battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed balancing control.

Evaluation of the impact of plug-in electric vehicle loading on distribution system operations

Abstract: Electric transportation has many attractive features in today's energy environment including decreasing greenhouse gas emissions from the transportation sector, reducing dependence on imported petroleum, and potentially providing consumers a lower cost alternative to gasoline. Plug-in hybrid Electric (PHEV) vehicles represent the most promising approach to electrification of a significant portion of the transportation sector. Electric power utilities recognize this possibility and must analyze the associated impacts to electric system operations. This paper provides details of analytical framework developed to evaluate the impact of PHEV loading on distribution system operations as part of a large, multi-utility collaborative study. This paper also summarizes partial results of the impact of PHEVs on one utility distribution feeder.

Reliable, long-haul data communications over power lines for meter reading and other communications services

Abstract: A system, method and computer program product provides for power line communications (PLC) over electric power lines includes a device mountable near an electrical distribution transformer (DT) to provide a high speed interface and communicates with one or multiple access devices, which provide low speed interfaces for analog signals or digital signals over RS 232, RS 485, optical, wireless and Ethernet. The device transmits data to/from these access devices over the electric lines to other repeaters over one or more wires of an electrical line or over multiple lines, and serves to strengthen and improve signal quality. Upon detecting a wire or line is having problems carrying data, the data is sent over other wires, and upon power line failures, wireless backup to mobile/GSM and WiMax networks is utilized. The device permits utilities and others to read electric meters, monitor the power quality of the distribution grid and detect power losses/failures/outages, and permits telecom service providers and others to provide a communications link to cell phone towers, WiFi Access Points and enable broadband Internet and telephony in rural, remote or sparely populated areas.

Power grid vulnerability: a complex network approach

Abstract: Power grids exhibit patterns of reaction to outages similar to complex networks. Blackout sequences follow power laws, as complex systems operating near a critical point. Here, the tolerance of electric power grids to both accidental and malicious outages is analyzed in the framework of complex network theory. In particular, the quantity known as efficiency is modified by introducing a new concept of distance between nodes. As a result, a new parameter called net-ability is proposed to evaluate the performance of power grids. A comparison between efficiency and net-ability is provided by estimating the vulnerability of sample networks, in terms of both the metrics.

Technique for conveying a wireless-standard signal through a barrier

Abstract: The RF signal generated by a ZigBee radio on the outside of a building structure is conveyed to the interior of the building by guiding it along an electric cable bundle that passes through the building's wall to supply domestic electric power to the interior of the structure. The RF signal is launched by a unique coupler comprising a pair of insulated foil conductors.

Using an electric power cable as the vehicle for communicating an information-bearing signal through a barrier

Abstract: The RF signal generated by a ZigBee radio on the outside of a building structure is conveyed to the interior of the building by guiding it as a surface wave along an electric cable bundle that passes through the building's wall to supply domestic electric power to the interior of the structure. The RF signal is launched by a unique coupler comprising a pair of insulated foil conductors.

Surface wave coupler

Abstract: The RF signal generated by a ZigBee radio on the outside of a building structure is conveyed to the interior of the building by guiding it along an electric cable bundle that passes through the building's wall to supply domestic electric power to the interior of the structure. The RF signal is launched by a unique coupler comprising a pair of insulated foil conductors.

Smart grid design for efficient and flexible power networks operation and control

Abstract: The modernization of the US electric power infrastructure, especially in lieu of its aging, overstressed networks; shifts in social, energy and environmental policies, and also new vulnerabilities, is a national concern. Our system are required to be more adaptive and secure more than every before. Consumers are also demanding increased power quality and reliability of supply and delivery. As such, power industries, government and national laboratories and consortia have developed increased interest in what is now called the Smart Grid of the future. The paper outlines Smart Grid intelligent functions that advance interactions of agents such as telecommunication, control, and optimization to achieve adaptability, self-healing, efficiency and reliability of power systems. The author also presents a special case for the development of Dynamic Stochastic Optimal Power Flow (DSOPF) technology as a tool needed in Smart Grid design. The integration of DSOPF to achieve the design goals with advanced DMS capabilities are discussed herein. This reference paper also outlines research focus for developing next generation of advance tools for efficient and flexible power systems operation and control.

Worst-Case Interdiction Analysis of Large-Scale Electric Power Grids

Abstract: This paper generalizes Benders decomposition to maximize a nonconcave objective function and uses that decomposition to solve an ldquoelectric power grid interdiction problem.rdquo Under one empirically verified assumption, the solution to this bilevel optimization problem identifies a set of components, limited by cardinality or ldquointerdiction resource,rdquo whose destruction maximizes economic losses to customers (and can thereby guide defensive measures). The decomposition subproblem typically incorporates a set of DC optimal power-flow models that cover various states of repair after an attack, along with a load-duration curve. Test problems describe a regional power grid in the United States with approximately 5000 buses, 6000 lines, and 500 generators. Solution time on a 2-GHz personal computer is approximately one hour.

Combining the Wind Power Generation System With Energy Storage Equipment

Abstract: With the advancements in wind turbine technologies, the cost of wind energy has become competitive with other fuel-based generation resources. Due to the price hike of fossil fuel and the concern of global warming, the development of wind power has rapidly progressed over the last decade. The annual growth rate has exceeded 26% since the 1990s. Many countries have set a goal for high penetration levels of wind generation. Recently, several large-scale wind generation projects have been implemented all over the world. It is economically beneficial to integrate very large amounts of wind capacity in power systems. Unlike other traditional generation facilities, using wind turbines presents technical challenges in producing continuous and controllable electric power. A distinct feature of wind energy is its nature of being ldquointermittent.rdquo Since it is difficult to predict and control the output of wind generation, its potential impacts on the electric grid are different from the traditional energy sources. At a high penetration level, an extrafast response reserve capacity is needed to cover the shortfall of generation when a sudden deficit of wind takes place. To enable a proper management of the uncertainty, this paper presents an approach to make wind power become a more reliable source on both energy and capacity by using energy storage devices. Combining the wind power generation system with energy storage will reduce fluctuation of wind power. Since it requires capital investment for the storage system, it is important to estimate the reasonable storage capacities for the desired applications. In addition, an energy storage application for reducing the output variation during the gust wind is also studied.

Thermoelectric Power Generation Using Waste-Heat Energy as an Alternative Green Technology

Abstract: In recent years, an increasing concern of environmental issues of emissions, in particular global warming and the limitations of energy resources has resulted in extensive research into novel technologies of generating electrical power. Thermoelectric power generators have emerged as a promising alternative green technology due to their distinct advantages. Thermoelectric power generation offer a potential application in the direct conversion of waste-heat energy into electrical power where it is unnecessary to consider the cost of the thermal energy input. The application of this alternative green technology in converting waste-heat energy directly into electrical power can also improve the overall efficiencies of energy conversion systems. In this paper, a background on the basic concepts of thermoelectric power generation is presented and recent patents of thermoelectric power generation with their important and relevant applications to waste-heat energy are reviewed and discussed.

Power line takeoff clamp assembly

Abstract: In a power line takeoff clamp assembly and method of use thereof an electrical power distribution line is clamped to a body of the clamp assembly. A power takeoff supported by the body clamped to the power line generates direct current from alternating current flowing in the power line. One or more sensors supported by the body clamped to the power line sense one or more values related to an electrical current flowing in a power line. A wireless transceiver supported by the body clamped to the power line communicates data regarding the one or more sensed values. Each sensor and the wireless transceiver utilize direct current generated by the power takeoff for the operation thereof.

The Effect of Non-linear Piezoelectric Coupling on Vibration-based Energy Harvesting

Abstract: Advances in electronic and consumer technology are increasing the need for smaller, more efficient energy sources Thus vibration-based energy harvesting, the scavenging of energy from existing ambient vibration sources and its conversion to useful electrical power, is becoming an increasingly attractive alternative to traditional power sources such as batteries Energy harvesting devices have been developed based on a number of electromechanical coupling mechanisms and their design must be optimized to produce the maximum output for given environmental conditions While the role of non-linearities in the components has been shown to be significant in terms of the overall device efficiency, few studies have systematically investigated their influence on the system performance In this work the role of a non-linear piezoelectric relationship is considered on the performance of a vibration-based energy harvester Using a Poincare-Lindstedt perturbation analysis the response of the harvesting system is appro

Ultracapacitor Technologies and Application in Hybrid and Electric Vehicles

Abstract: This paper focuses on ultracapactors (electrochemical capacitors) as energy storage in vehicle applications and thus evaluates the present state-of-the-art of ultracapacitor technologies and their suitability for use in electric and hybrid drivelines of various types of vehicles. A key consideration in determining the applicability of ultracapacitors for a particular vehicle application is the proper assessment of the energy storage and power requirements. For hybrid-electric vehicles, the key issues are the useable energy requirement and the maximum pulse power at high efficiency. For a Prius size vehicle, if the useable energy storage is about 125 Wh and needed efficiency is 90-95%, analysis shown in this paper indicate that vehicles can be designed using carbon ultracapacitors (both carbon/carbon and hybrid carbon) that yield high fuel economy improvements for all driving cycles and the cost of the ultracapacitors can be competitive with lithium-ion batteries for high volume production and carbon prices of less than $20/kg. The use of carbon/carbon devices in micro-hybrids is particularly attractive for a control strategy (sawtooth) that permits engine operation near its maximum efficiency using only a 6 kW electric motor. Vehicle projects in transit buses and passenger cars have shown that ultracapacitors have functioned as expected and significant fuel economy improvements have been achieved that are higher than would have been possible using batteries because of the higher round-trip efficiencies of the ultracapacitors. Ultracapacitors have particular advantages for use in fuel cell powered vehicles in which it is likely they can be used without interface electronics. Development of hybrid carbon devices is continuing showing energy densities of 12 Wh/kg and a high efficiency power density of about 1000 W/kg. Vehicle simulations using those devices have shown that increased power capability in such devices is needed before full advantage can be taken of their increased energy density compared to carbon/carbon devices in some vehicle applications. Energy storage system considerations indicate that combinations of ultracapacitors and advanced batteries (Wh/kg>200) are likely to prove advantageous in the future as such batteries are developed. This is likely to be the case in plug-in hybrids with high power electric motors for which it may be difficult to limit the size and weight of the energy storage unit even using advanced batteries.

Paying the price for unreliable power supplies : in-house generation of electricity by firms in Africa

Abstract: This paper documents the prevalence of in-house generation of electric power by firms in Sub-Saharan Africa and attempts to identify the underlying causes. The analysis is based on two data sources. The UDI World Electric Power Plants Data Base (WEPP), a global inventory of electric power generating units, provides a detailed inventory of in-house generation at the country level. The World Bank's Enterprise Survey Database captures business perceptions of the obstacles to enterprise growth for 8,483 currently operating firms in 25 African countries. Overall, so-called own generation by firms-which has been on the rise in recent years-accounts for about 6 percent of installed generation capacity in Sub-Saharan Africa (equivalent to at least 4,000 MW of installed capacity). However, this share doubles to around 12 percent in the low-income countries, the post-conflict countries, and more generally on the Western side of the continent. In a handful of countries own generation represents more than 20 percent of capacity. Rigorous empirical analysis shows that unreliable public power supplies is far from being the only or even the largest factor driving generator ownership. Firm characteristics have a major influence-in particular, the probability of owning a generator doubles in large firms relative to small ones. Our model predicts that the prevalence of own generation would remain high (at around 20 percent) even if power supplies were perfectly reliable, suggesting that other factors, such as emergency back-up and export regulations, play a critical role in the decision to own a generator.

Noncontact electric power receiving device, noncontact electric power transmitting device, noncontact electric power feeding system, and electrically powered vehicle

Abstract: A first shielding box is disposed so that its first surface can be opposite to an electric power feeding unit. The first surface has an opening and remaining five surfaces thereof reflect, during reception of electric power from the electric power feeding unit, a resonant electromagnetic field (near field) generated in the surroundings of the electric power receiving unit. The electric power receiving unit is provided in the first shielding box to receive the electric power from the electric power feeding unit via the opening (first surface) of the first shielding box. A second shielding box has a similar configuration, i.e., has a second surface with an opening and remaining five surfaces thereof reflect the resonant electromagnetic field (near field) generated in the surroundings of the electric power feeding unit.

A review on reliability assessment for wind power

Abstract: The application of wind energy in electric power systems is growing rapidly due to enhanced public concerns to adverse environmental impacts and escalation in energy costs associated with the use of conventional energy sources. Electric power from wind energy is quite different from that of conventional resources. The fundamental difference is that the wind power is intermittent and uncertain. Therefore, it affects the reliability of power system in a different manner from that of the conventional generators. This paper, from available literatures, presents the model of wind farms and the methods of wind speed parameters assessment. Two main categories of methods for evaluating the wind power reliability contribution, i.e., the analytical method and the Monte Carlo simulation method have been reviewed. This paper also summarizes factors affecting the reliability of wind power system, such as wake effect, correlation of output power for different windturbines, effect of windturbine parameters, penetration and environment. An example has been used to illustrate how these factors affect the reliability of wind power system. Finally, mainstream reliability indices for evaluating reliability are introduced. Among these reliability indices, some are recently developed, such as wind generation interrupted energy benefit (WGIEB), wind generation interruption cost benefit (WGICB), Equivalent Capacity Rate (ECR), load carrying capacity benefit ratio (LCCBR).

Power system harmonics research: a survey

Abstract: The increased use of power electronic controlled equipment, such as variable speed drives, automated production lines, personal computers and non-linear electronic devices in power systems has given rise to a type of voltage and current waveform distortion called as ‘harmonics’. Harmonic can be defined as the undesirable components of a distorted periodic waveform whose frequencies are the integer multiples (non-integer multiples in case of inter-harmonics, and the frequency less than fundamental frequency in case of sub-harmonics) of the fundamental frequency. Presence of these harmonics results in increased losses, equipment heating and loss-of-life, and interference with protection, control and communication circuits as well as customer loads. The research has been underway since very beginning for control of power system harmonics and to supply consumers with reliable and ‘clean’ fundamental-frequency sinusoidal electric power that does not represent a damaging threat to their equipment. This paper, therefore, reviews the progress made in power system harmonics research and development since its inception. Attempts are also made to highlight the current and future issues involved in the development of quality and reliable electric power technology for future applications. A list of 145 research publications on the subject is also appended for a quick reference. Copyright © 2007 John Wiley & Sons, Ltd.

Air Emissions Due To Wind And Solar Power

Abstract: Renewables portfolio standards (RPS) encourage large-scale deployment of wind and solar electric power. Their power output varies rapidly, even when several sites are added together. In many locations, natural gas generators are the lowest cost resource available to compensate for this variability, and must ramp up and down quickly to keep the grid stable, affecting their emissions of NOx and CO2. We model a wind or solar photovoltaic plus gas system using measured 1-min time-resolved emissions and heat rate data from two types of natural gas generators, and power data from four wind plants and one solar plant. Over a wide range of renewable penetration, we find CO2 emissions achieve ∼80% of the emissions reductions expected if the power fluctuations caused no additional emissions. Using steam injection, gas generators achieve only 30−50% of expected NOx emissions reductions, and with dry control NOx emissions increase substantially. We quantify the interaction between state RPSs and NOx constraints, find...

Wirless power supply device

Abstract: A wireless power supply device is adapted for providing electric power to an exterior electronic appliance. The wireless power supply includes a transmitting unit and a receiving unit. The transmitting unit includes a power unit for providing power to a voltage-controlled oscillator circuit and a signal amplification unit, the voltage-controlled oscillator circuit for receiving the power and then generating corresponding radio signals, the signal amplification unit for amplifying the radio signals generated by the voltage-controlled oscillator circuit and a transmitting antenna module for transmitting out the radio signals amplified by the signal amplification unit. The receiving unit includes a receiving antenna for wirelessly receiving the radio signals transmitted by the transmitting antenna module and then transforming the radio signals into electric power for being provided to the exterior electronic appliance.

Transmission alternatives for offshore electrical power

Abstract: The oceans represent a huge energy reservoir. Although today all of the marine power projects are very near from the shore and they are rated at low power, the huge potential of the seas may in a not very distant future bring marine power further into the sea. Also offshore oil and gas exploration is moving into deeper waters and at longer distances from land. New carbon sequestration projects under the seabed are on the way which require a vast amount of electric power consumption. The substitution of offshore power generators by power provided from the grid may have environmental benefits, but the deployment of offshore transmission of bulk electrical power to or from offshore platforms to the electrical grid onshore is a mayor challenge. The main objective of this paper is to focus on trends that can lead to a feasible transmission system in offshore energy systems far from land, and to introduce the technological alternatives which could help to reach that goal. The paper describes the main alternatives and the technical and economical aspects of the transmission of electrical power offshore.